HEARING - sensation and perception

What is sound and how do we experience it?

vibrations that travel through a medium (like air) and are interpreted by our ears as auditory info

What is frequency and amplitude?

frequency: how fast sound waves vibrate per second (measured in Hertz (Hz))

• determines pitch (high sound vs. low sound)

  • high frequency → high pitch

  • low frequency → low pitch

What are the three divisions of the ear?

outer ear, middle ear, inner ear

What is the outer ear and what does it consist of?

the outer ear collects sound waves and funnels them toward the middle ear

• Pinna: the visible part of the ear that captures sound and helps determine sound direction

• Ear canal (auditory canal): tube that channels sound waves from the pinna to the ear drum (tympanic membrane)

gathers and directs sounds to the middle ear which amplifies it

What is the middle ear and what does it consist of?

applies and transmits sound vibrations from the outer ear to the inner ear

• tympanic membrane (eardrum) : vibrates when sound waves hit it

turns sound waves into vibrations to pass to the inner ear

What is the inner ear and what does it consist of?

inner ear converts mechanical sound vibrations into neural signals that the brain can interpret

• oval window: connects to the middle ear to the cochlea and transmits vibrations to the cochlear fluid

• cochlea: spiral shaped, fluid filled structure where sound waves are converted into movement along the basilar membrane

• basilar membrane: runs through the cochlea and has hair cells on it which detect different frequencies and transduce them into neural signals

• auditory nerve: connects chela to the brain where the neural signals created by hair cells are transmitted

What is place theory of pitch detection?

explains how we perceive pitch based on where along the basilar membrane the hair cells are stimulated

• different parts of the basilar membrane respond to different frquencies

  • high frquencies is the base of the cohlea

  • low is near the end

• so when the hair cells of that area send neural signals the brain perceives different pitches 

“where’’ along the basilar membrane determines pitch

What is Frequency of pitch detection?

How we perceive low-pitched sounds based on the rate at which hair cells on the basilar membrane fire

• if they are firing slower its a low pitch

How does the brain process auditory information

once the hair cells transduce into neural signals it gets taken to the auditory cortex processor is located in the temporal lobe which interprets the pitch, loudness, location of sound

How can we tell where sound comes from?

• sound reaches one ear slightly before

  • sound is also louder in the ear closer to the source

• brain compares timing to determine left vs. right

What is stereophonic or three-dimensional hearing?

stereophonic hearing allows us to perceive sound in three dimensions

• Intramural tme difference (ITD): sound reaches one ear before

• Intramural intensity difference (IID) sound is louder in the ear closer to the source

What is soundscape awareness?

ability to perceive, identify, and interpret the range of sounds in an environment

• its about understanding your auditory environment, not just hearing isolated soundsW

What’s Volley principal

explains how we perceive higher pitched sounds that individual neurons cannot fire fast enough to follow

• allow perception of frequencies above 1000 Hz because neurons take turns firing in rapid succession